Ultrasonic-assisted flocculation and sedimentation of coal slime water using the Taguchi method

Abstract

ABSTRACT As the intensity of mining increases, the gangue content in coal slime water increases, leading to difficulties in settling suspended particles. In recent years, ultrasound technology has received much attention in the field of water treatment due to its high efficiency and convenience, and coal slime water undergoes ultrasonic pretreatment to improve flocculation. This study explored the effects of four factors, namely ultrasonic power, ultrasonic time, flocculant dosage, and coal slime water concentration, on the flocculation efficiency of coal slime water using an orthogonal design. The optimum conditions for ultrasound-assisted coal slime water flocculation were found to be an ultrasonic power value of 192 W, an ultrasonic time of 8 min, pH 8, a flocculant dosage of 24 mg/L, and a coal slime water concentration of 30 g/L. The flocculation efficiency reached 92.64%. After a certain time of ultrasonic pretreatment (8 min), there was a reduction in the amount of clay on the surface of the coal slime particles, the potential decreased to −3.07 mV, and the average and fractal sizes of the flocs were 80.45 µm and 2.01, respectively. A range of methods was used to confirm that the settling effect of the coal slime water had been improved by ultrasonic pretreatment.